ASHRAE Journal - November 2014 - 66

envelope. Existing walls were insulated with R-11 fiberglass. Some exterior walls were furred out and brought
up to R-19. The roof is insulated to only R-20 (no work
was done on the roof). These insulation levels are well
below current Washington State Energy Code for new
construction and below Standard 90.1-2007 requirements. After a cost-benefit analysis, it was determined
that investing in a high performance HVAC system
could offset the relatively poor performance of the
building envelope.

EUI (kBtu/ft2 · yr)

2014 ASHRAE TECHNOLOGY AWARD CASE STUDIES

90
80
70
60
50
40
30
20
10
0

Plugs/Fans

Lights

Cool

Heat

26.7
KCHA Existing Office

KCHA Central Annex

FIGURE 1 KCHA energy use comparison.

Dedicated Outdoor Air System
The VCHP system achieves an average annual COP of
The built up energy recovery ventilation (ERV) system
about 3.0 in heating without the need for any auxiliary
was designed and selected for very low fan energy and
heat source. The heat pumps maintain nearly full output
high heat recovery effectiveness. The ECM fans provide
capacity to temperatures well below Seattle's outdoor
100% outdoor air ventilation at less than 0.75 W/cfm.
heating design temperature of 24°F (-4°C). The building
The ERV system needs only small (inexpensive) ducts to
deliver air directly to all habitable spaces while continu- includes both interior and perimeter zones and during
the swing seasons the VCHP system
ously exhausting stale air from spehas the ability to provide direct heat
cific high pollution locations (conferrecovery if some zones are in heatence rooms, large offices, restrooms,
HVAC
$14
ing while others are in cooling. While
kitchen, copy room, janitor, server
the VCHP heat recovery option has
room) during occupied hours.
Electrical
$13
the potential to significantly increase
The apparent sensible heat recovery
Other
efficiency, in practice we have found
effectiveness of the ERV is greater
$64
Plumbing
that the system rarely enters this heat
than 86%. This allowed the elimina$2
recovery mode. When the building
tion of a reheat system in the ventilaFire Protection
loads are controlled, the true benefits
tion supply airstream. Even at design$2
of VCHP are realized: excellent effiday temperatures (24°F [-4°C]), the
FIGURE 2 KCHA construction budget ($/ft2).
ciency at full and part load operation
ERV delivery temperature is in the
and low fan power energy. No DDC
60s.
system was needed as the VCHP control system was used
as the building control system for the ERV and heating
Zoning for Energy Efficiency and Control
and cooling scheduling.
The variable capacity heat pump (VCHP) system was
designed with 50 discreet control zones, allowing for a
high degree of individual occupant control and comfort. Indoor Environmental Quality
Indoor environmental quality was an important design
Since the design completely separates the ventilation
requirement expressed by the client in the predesign
system from the heating and cooling system, this allows
phases. The project sought to provide ample filtered outthe fans for the zonal VCHP system to cycle only when
there is a call for heating or cooling in the serviced zone. door air, low off-gassing materials, daylighting in main
circulation spaces, low noise variable speed equipment,
Fan energy for the delivery of heating and cooling is
thereby reduced to a small fraction of a typical building. and occupant control of their spaces.
The building uses three highly efficient counter-flow
In addition, most spaces are served with ductless T-bar
ceiling mounted indoor heat pump equipment. Ductless air-to-air energy recovery ventilators for all zones, with
100% outdoor air sized per Standard 62.1-2010. Budget
high efficiency fans in this equipment operate at a
constraints didn't allow for variable airflow volumes
small fraction of the fan energy required by typical fully
in conference rooms and modeling confirmed that the
ducted fan coil systems or VAV systems.
66

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ASHRAE Journal - November 2014

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